Solid oxide fuel cells each include a power-generating element unit composed of a fuel electrode layer, an oxygen electrode layer, and a solid electrolyte layer sandwiched therebetween.
A solid oxide fuel cell is configured as follows: for example, such a power-generating element unit is formed on an electrically conductive support which is porous and which has gas channels extending therein, an interconnector is formed on the electrically conductive support that is free from the solid electrolyte layer, and the electrically conductive support is surrounded by the solid electrolyte layer and the interconnector.
Hydrogen is supplied to a fuel electrode layer from the electrically conductive support by feeding a fuel gas (for example, a hydrogen gas) through the gas channels in the electrically conductive support while oxygen is supplied to an oxygen electrode layer by feeding an oxygen-containing gas such as air to an outer surface of the oxygen electrode layer. This causes an electrode reaction on each electrode. The current generated thereby is extracted using the interconnector placed on the electrically conductive support (for example, Patent Literature 1).
Each of cell stacks is configured by connecting a plurality of such fuel cells to each other in series. The cell stacks are housed in a storage vessel and are connected to each other through electrically conductive members, whereby a fuel cell module is configured.
The following is a list of the aforementioned background art PTL 1: Japanese Unexamined Patent Application Publication No. 2004-146334
However, in the conventional fuel cell disclosed in Japanese Unexamined Patent Application Publication No. 2004-146334, the solid electrolyte layer and the interconnector need to be dense because the electrically conductive support is surrounded by the solid electrolyte layer and the interconnector such that the fuel gas supplied into the electrically conductive support does not leak out. In addition, in flat and cylindrical fuel cells, solid electrolyte layers and interconnectors need to be dense such that fuel gases supplied to electrically conductive supports do not leak out. In order to prepare such a dense solid electrolyte layer and interconnector, the agglomeration of raw materials needs to be prevented, the raw materials need to be controlled by reducing dust and impurities, and, furthermore, manufacturing steps need to be strictly controlled. Thus, there is a problem in that it takes time and manpower to prevent gas from leaking from a solid electrolyte layer or an interconnector.
It is an object of the present invention to provide a solid oxide fuel cell capable of readily preventing the leakage of gas, a fuel cell stack device, a fuel cell module, and a fuel cell apparatus.